1. Field of the Invention
The present invention relates to a chemical dispenser for a body of water, and more specifically to a chlorinator for a cartridge-type pool or spa filter and also to a chemical dispenser utilizing an air load principle for regulating the concentration of chemical dispensed to the pool or spa.
2. Related Art
Cartridge-type pool filters are well known in the art. The filter includes a canister or tank for containing a hollow cylindrical filter element. The housing has a fluid inlet and a fluid outlet in the bottom and the cylindrical filter element fits around a perforated standpipe extending upward from the bottom of the tank. Water flows into the tank and up the sides of the container along the outside of the filter element. Because the incoming water is pressurized a pressure gradient exists across the filter element, and the water is forced substantially radially through the circumferential portion of the cylindrical filter element to the interior of the filter element. The outlet pressure is lower than the inlet pressure so that the filtered water passes from the interior of the filter element through the perforated standpipe and to the outlet.
A variant of the filter described above has the inlet and outlet connections to the filter located at the upper end of the filter housing. If desired, all or only a portion of the water supplied to the housing inlet is routed to the filter chamber for flow through the filter element. Usually such flow diversion is determined by a pressure responsive mechanism which, in cases where the filter is used in a spa having a two-spaced water circulating pump, reacts to high pump pressure to shunt a major portion of the inlet water flow direct to the outlet from the filter. Such a filter is the Dynamic Series Model RDC-25 spa/pool in-line cartridge filter manufactured by the Rainbow Plastics Filter Division of the assignee of this invention.
Regardless of the specific nature of the cartridge filter structure, it is coupled to the high pressure or discharge side of a spa or pool circulation pump which, most often, operates on a daily cycle under control by a timer.
Chemicals for swimming pool use come in a variety of forms. Chlorine is commonly used in swimming pools and is available in granules, tablets and concentrated liquid. Some of the chemicals may be introduced by hand or by elaborate automatic mechanical devices. Additionally, the chemicals may be introduced using float packages similar to those shown in U.S. Pat. Nos. 3,677,711 and 4,217,331.
Particularly in spa systems, it is desirable that the filter and chlorinator structure be as compact as possible. Heretofore, so far as is known, chlorinators have either been provided as units separate from filters but used with the filters, or as add-on assemblies mountable to the top of the filter so as to increase the height of the filter. A need exists for a chlorinator arrangement which can be located wholly within the envelope otherwise provided for the filter. This invention addresses that need and has particular utility in the context of filters used with spas.